The theories of epipolar lines have particular significance for the development of digital photogrammetry , which make the task of searching conjugate points from stereo images an one-dimensional problem. As a result, methods to determine the conjugate epipolar lines is discussed in many papers. SLL(Sloping Line Locus) is presented in this paper as an extension of VLL(Vertical Line Locus ) method. Then, based on SLL and geometric characteristics of epipolar point, this paper proposes two new methods to determine conjugate epipolar lines .The new methods are simple in theory and have explicit geometric relationship, which makes them easily applicable.